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<div class="titlepage"><div><div><h3 class="title">
<a name="boost_asio.reference.deadline_timer"></a><a class="link" href="deadline_timer.html" title="deadline_timer">deadline_timer</a>
</h3></div></div></div>
<p>
        <a class="indexterm" name="boost_asio.indexterm.deadline_timer"></a> 
Typedef for the typical
        usage of timer. Uses a UTC clock.
      </p>
<pre class="programlisting">typedef basic_deadline_timer&lt; boost::posix_time::ptime &gt; deadline_timer;
</pre>
<h5>
<a name="boost_asio.reference.deadline_timer.h0"></a>
        <span class="phrase"><a name="boost_asio.reference.deadline_timer.types"></a></span><a class="link" href="deadline_timer.html#boost_asio.reference.deadline_timer.types">Types</a>
      </h5>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
</colgroup>
<thead><tr>
<th>
                <p>
                  Name
                </p>
              </th>
<th>
                <p>
                  Description
                </p>
              </th>
</tr></thead>
<tbody>
<tr>
<td>
                <p>
                  <a class="link" href="basic_deadline_timer__rebind_executor.html" title="basic_deadline_timer::rebind_executor"><span class="bold"><strong>rebind_executor</strong></span></a>
                </p>
              </td>
<td>
                <p>
                  Rebinds the timer type to another executor.
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
                  <a class="link" href="basic_deadline_timer/duration_type.html" title="basic_deadline_timer::duration_type"><span class="bold"><strong>duration_type</strong></span></a>
                </p>
              </td>
<td>
                <p>
                  The duration type.
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
                  <a class="link" href="basic_deadline_timer/executor_type.html" title="basic_deadline_timer::executor_type"><span class="bold"><strong>executor_type</strong></span></a>
                </p>
              </td>
<td>
                <p>
                  The type of the executor associated with the object.
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
                  <a class="link" href="basic_deadline_timer/time_type.html" title="basic_deadline_timer::time_type"><span class="bold"><strong>time_type</strong></span></a>
                </p>
              </td>
<td>
                <p>
                  The time type.
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
                  <a class="link" href="basic_deadline_timer/traits_type.html" title="basic_deadline_timer::traits_type"><span class="bold"><strong>traits_type</strong></span></a>
                </p>
              </td>
<td>
                <p>
                  The time traits type.
                </p>
              </td>
</tr>
</tbody>
</table></div>
<h5>
<a name="boost_asio.reference.deadline_timer.h1"></a>
        <span class="phrase"><a name="boost_asio.reference.deadline_timer.member_functions"></a></span><a class="link" href="deadline_timer.html#boost_asio.reference.deadline_timer.member_functions">Member Functions</a>
      </h5>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
</colgroup>
<thead><tr>
<th>
                <p>
                  Name
                </p>
              </th>
<th>
                <p>
                  Description
                </p>
              </th>
</tr></thead>
<tbody>
<tr>
<td>
                <p>
                  <a class="link" href="basic_deadline_timer/async_wait.html" title="basic_deadline_timer::async_wait"><span class="bold"><strong>async_wait</strong></span></a>
                </p>
              </td>
<td>
                <p>
                  Start an asynchronous wait on the timer.
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
                  <a class="link" href="basic_deadline_timer/basic_deadline_timer.html" title="basic_deadline_timer::basic_deadline_timer"><span class="bold"><strong>basic_deadline_timer</strong></span></a> <span class="silver">[constructor]</span>
                </p>
              </td>
<td>
                <p>
                  Constructor. <br> <span class="silver"> —</span><br> Constructor to set a particular expiry
                  time as an absolute time. <br> <span class="silver"> —</span><br> Constructor to set a particular
                  expiry time relative to now. <br> <span class="silver"> —</span><br> Move-construct a basic_deadline_timer
                  from another.
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
                  <a class="link" href="basic_deadline_timer/cancel.html" title="basic_deadline_timer::cancel"><span class="bold"><strong>cancel</strong></span></a>
                </p>
              </td>
<td>
                <p>
                  Cancel any asynchronous operations that are waiting on the timer.
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
                  <a class="link" href="basic_deadline_timer/cancel_one.html" title="basic_deadline_timer::cancel_one"><span class="bold"><strong>cancel_one</strong></span></a>
                </p>
              </td>
<td>
                <p>
                  Cancels one asynchronous operation that is waiting on the timer.
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
                  <a class="link" href="basic_deadline_timer/expires_at.html" title="basic_deadline_timer::expires_at"><span class="bold"><strong>expires_at</strong></span></a>
                </p>
              </td>
<td>
                <p>
                  Get the timer's expiry time as an absolute time. <br> <span class="silver"> —</span><br>
                  Set the timer's expiry time as an absolute time.
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
                  <a class="link" href="basic_deadline_timer/expires_from_now.html" title="basic_deadline_timer::expires_from_now"><span class="bold"><strong>expires_from_now</strong></span></a>
                </p>
              </td>
<td>
                <p>
                  Get the timer's expiry time relative to now. <br> <span class="silver"> —</span><br> Set
                  the timer's expiry time relative to now.
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
                  <a class="link" href="basic_deadline_timer/get_executor.html" title="basic_deadline_timer::get_executor"><span class="bold"><strong>get_executor</strong></span></a>
                </p>
              </td>
<td>
                <p>
                  Get the executor associated with the object.
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
                  <a class="link" href="basic_deadline_timer/operator_eq_.html" title="basic_deadline_timer::operator="><span class="bold"><strong>operator=</strong></span></a>
                </p>
              </td>
<td>
                <p>
                  Move-assign a basic_deadline_timer from another.
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
                  <a class="link" href="basic_deadline_timer/wait.html" title="basic_deadline_timer::wait"><span class="bold"><strong>wait</strong></span></a>
                </p>
              </td>
<td>
                <p>
                  Perform a blocking wait on the timer.
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
                  <a class="link" href="basic_deadline_timer/_basic_deadline_timer.html" title="basic_deadline_timer::~basic_deadline_timer"><span class="bold"><strong>~basic_deadline_timer</strong></span></a> <span class="silver">[destructor]</span>
                </p>
              </td>
<td>
                <p>
                  Destroys the timer.
                </p>
              </td>
</tr>
</tbody>
</table></div>
<p>
        The <a class="link" href="basic_deadline_timer.html" title="basic_deadline_timer"><code class="computeroutput">basic_deadline_timer</code></a>
        class template provides the ability to perform a blocking or asynchronous
        wait for a timer to expire.
      </p>
<p>
        A deadline timer is always in one of two states: "expired" or "not
        expired". If the <code class="computeroutput">wait()</code> or <code class="computeroutput">async_wait()</code> function
        is called on an expired timer, the wait operation will complete immediately.
      </p>
<p>
        Most applications will use the <a class="link" href="deadline_timer.html" title="deadline_timer"><code class="computeroutput">deadline_timer</code></a>
        typedef.
      </p>
<h5>
<a name="boost_asio.reference.deadline_timer.h2"></a>
        <span class="phrase"><a name="boost_asio.reference.deadline_timer.thread_safety"></a></span><a class="link" href="deadline_timer.html#boost_asio.reference.deadline_timer.thread_safety">Thread
        Safety</a>
      </h5>
<p>
        <span class="emphasis"><em>Distinct</em></span> <span class="emphasis"><em>objects:</em></span> Safe.
      </p>
<p>
        <span class="emphasis"><em>Shared</em></span> <span class="emphasis"><em>objects:</em></span> Unsafe.
      </p>
<h5>
<a name="boost_asio.reference.deadline_timer.h3"></a>
        <span class="phrase"><a name="boost_asio.reference.deadline_timer.examples"></a></span><a class="link" href="deadline_timer.html#boost_asio.reference.deadline_timer.examples">Examples</a>
      </h5>
<p>
        Performing a blocking wait:
      </p>
<pre class="programlisting">// Construct a timer without setting an expiry time.
boost::asio::deadline_timer timer(my_context);

// Set an expiry time relative to now.
timer.expires_from_now(boost::posix_time::seconds(5));

// Wait for the timer to expire.
timer.wait();
</pre>
<p>
        Performing an asynchronous wait:
      </p>
<pre class="programlisting">void handler(const boost::system::error_code&amp; error)
{
  if (!error)
  {
    // Timer expired.
  }
}

...

// Construct a timer with an absolute expiry time.
boost::asio::deadline_timer timer(my_context,
    boost::posix_time::time_from_string("2005-12-07 23:59:59.000"));

// Start an asynchronous wait.
timer.async_wait(handler);
</pre>
<h5>
<a name="boost_asio.reference.deadline_timer.h4"></a>
        <span class="phrase"><a name="boost_asio.reference.deadline_timer.changing_an_active_deadline_timer_s_expiry_time"></a></span><a class="link" href="deadline_timer.html#boost_asio.reference.deadline_timer.changing_an_active_deadline_timer_s_expiry_time">Changing
        an active deadline_timer's expiry time</a>
      </h5>
<p>
        Changing the expiry time of a timer while there are pending asynchronous
        waits causes those wait operations to be cancelled. To ensure that the action
        associated with the timer is performed only once, use something like this:
        used:
      </p>
<pre class="programlisting">void on_some_event()
{
  if (my_timer.expires_from_now(seconds(5)) &gt; 0)
  {
    // We managed to cancel the timer. Start new asynchronous wait.
    my_timer.async_wait(on_timeout);
  }
  else
  {
    // Too late, timer has already expired!
  }
}

void on_timeout(const boost::system::error_code&amp; e)
{
  if (e != boost::asio::error::operation_aborted)
  {
    // Timer was not cancelled, take necessary action.
  }
}
</pre>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
            The <code class="computeroutput">boost::asio::basic_deadline_timer::expires_from_now()</code>
            function cancels any pending asynchronous waits, and returns the number
            of asynchronous waits that were cancelled. If it returns 0 then you were
            too late and the wait handler has already been executed, or will soon
            be executed. If it returns 1 then the wait handler was successfully cancelled.
          </li>
<li class="listitem">
            If a wait handler is cancelled, the boost::system::error_code passed
            to it contains the value <code class="computeroutput">boost::asio::error::operation_aborted</code>.
          </li>
</ul></div>
<h5>
<a name="boost_asio.reference.deadline_timer.h5"></a>
        <span class="phrase"><a name="boost_asio.reference.deadline_timer.requirements"></a></span><a class="link" href="deadline_timer.html#boost_asio.reference.deadline_timer.requirements">Requirements</a>
      </h5>
<p>
        <span class="emphasis"><em>Header: </em></span><code class="literal">boost/asio/deadline_timer.hpp</code>
      </p>
<p>
        <span class="emphasis"><em>Convenience header: </em></span><code class="literal">boost/asio.hpp</code>
      </p>
</div>
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
<td align="left"></td>
<td align="right"><div class="copyright-footer">Copyright © 2003-2021 Christopher
      M. Kohlhoff<p>
        Distributed under the Boost Software License, Version 1.0. (See accompanying
        file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
      </p>
</div></td>
</tr></table>
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